A suicide car bomber killed three policemen early on Thursday, Feb 14 morning in an attack in Russia’s North Caucasus republic of Dagestan, according to RIA Novosti.

The bomber detonated explosives as the police stopped his car at a checkpoint outside the city of Khasavyurt around 5 am, local police said.

Three police officers and the bomber died at the scene, while six injured policemen were rushed to hospital and another was reported missing. The blast left “a crater four meters in diameter and 1.5 meters deep,” the Investigative Committee said in a statement.

The Committee opened a criminal case on terrorism charges. No one has yet claimed responsibility for the attack.

Dagestan and most of the neighboring North Caucasus has suffered years of armed conflict between Islamist insurgents and the security forces, with frequent bombings and shootings.